1. Field of the Invention
The present invention relates to an information recording and reproduction apparatus for recording and reproducing information to and from a recording medium such as an optical disk. More particularly, the present invention relates to an information recording and reproduction apparatus having a highly reliable verification operation for verifying the recording condition of a recording medium.
2. Description of the Related Art
Recently, for data recording media, there is a demand for a higher level of recording density. In the case of high-density data recording media, a reproduced signal may have a low level of S/N (signal-to-noise) ratio or a non-linear waveform. Correct data needs to be obtained from such reproduced signals.
Examples of a known method for reproducing information recorded in (or on) a recording medium includes the following methods (1) through (3):
(1) a method in which a reproduced signal is equalized and then changed into binary form (hereinafter referred to as xe2x80x9creproduction equalization and binary methodxe2x80x9d);
(2) a method in which the waveform of a reproduced signal is shaped by partial response equalization, and a level of the shaped signal is detected, thereby reproducing information (hereinafter referred to as xe2x80x9cPR equalization and level detection methodxe2x80x9d); and
(3) a method in which information is reproduced by a combination of the PR equalization for waveform shaping of a reproduced signal, and a Viterbi decoding method which is one of so-called maximum likelihood decoding methods (hereinafter referred to as xe2x80x9cPR equalization and Viterbi decoding methodxe2x80x9d).
PRML (Partial Response Maximum Likelihood) methods, such as the PR equalization and Viterbi decoding method, can reduce errors which occur in data reproduction to considerable extent, compared to the conventional reproduction equalization and binary method and the PR equalization and level detection method. Therefore, the PRML method is widely used in techniques for processing signals recorded in high-density recording devices, such as an HDD (hard disk drive), a camera-recorder having a digital recording system, and a rewritable optical disk.
As for a removable medium such as an optical disk, there may be a high level of variation in a characteristic between individual disks or optical disk apparatuses. Conditions upon recording (recording condition) need to be optimized in order to prevent errors from occurring when information is reproduced from the same disk by optical disk apparatuses having different characteristics.
In an optical disk apparatus or the like, recorded data is read out, for example, in a verification operation after data recording, in format checking, in data reproduction, and the like. If the PR equalization and Viterbi decoding method is used every time recorded data is read out, the recorded data can be correctly reproduced even when the recording condition is not good (i.e., an error is likely to occur in reproduction). This is not always beneficial. In the verification operation after data recording, the recording condition is checked by detecting an error. When the PR equalization and Viterbi decoding method is used in the verification operation, a poor recording condition may be overlooked. Therefore, the verification operation is less reliable.
Japanese Laid-open Publication No. 9-55030 discloses a technique for solving such a problem. In the technique disclosed in Japanese Laid-open Publication No. 9-55030, either the PR equalization and level detection method or the PR equalization and Viterbi decoding method is used upon normal reproduction, while the reproduction equalization and binary method is used upon a verification operation. In this case, whereas an error rate in normal reproduction is reduced, a recording condition can be checked more strictly. Alternatively, there is a known technique in which the PR equalization and Viterbi decoding method is used upon normal reproduction, while the PR equalization and level detection method is used upon a verification operation.
In an optical disk having physical addresses (PID) such as prepit addresses, the optimal focus position of an optical head in reading data from a physical address region differs from that in reading data from a data region. In this case, if the focus position of the optical head is optimized for the data region, the optical head is defocused upon reading data from the physical address region and therefore an error is likely to occur. When either the PR equalization and level detection method or the PR equalization and Viterbi decoding method is used upon a verification operation as in conventional techniques, an address may fail to be precisely reproduced. If an address is not precisely reproduced, the recording condition is not correctly checked, thereby causing the verification operation to be less reliable.
According to one aspect of the present invention, an information recording and reproduction apparatus comprises: a recording section for recording data into a recording medium in accordance with address information recorded in the recording medium; a first reproduction section for reproducing at least one data including the data recorded in the recording medium in accordance with a first reproduction method to obtain at least one reproduced data; a second reproduction section for reproducing the address information in accordance with a second reproduction method to obtain reproduced address information; and a determination section for mapping the data to a specific reproduced data of the at least one reproduced data based on the address information and the reproduced address information, and comparing the data with the specific reproduced data to determine a recording condition of a region of the recording medium storing the data. The degree of influence of the recording condition of data recorded in the recording medium, on whether the data is correctly reproduced, is greater when the data is reproduced in accordance with the first reproduction method than with the second reproduction method.
In one embodiment of this invention, the address information is previously recorded in the form of a prepit in the recording medium.
In one embodiment of this invention, the recording section further records the address information into the recording medium,
In one embodiment of this invention, the data is recorded as a recorded signal in the recording medium, the information recording and reproduction apparatus further comprises an amplitude detection section for detecting an amplitude of the recorded signal, and the determination section performs determination of the recording condition, depending on whether the amplitude detected by the amplitude detection section is greater than a predetermined amplitude.
In one embodiment of this invention, the data is recorded as a first recorded signal in the recording medium. In the first reproduction method, the first recorded signal is equalized in accordance with a partial response method, and thereafter the equalized first recorded signal is subjected to level detection to obtain the first reproduced data. The address information is recorded as a second recorded signal in the recording medium. In the second reproduction method, the second recorded signal is equalized in accordance with the partial response method, and thereafter the equalized second recorded signal is subjected to Viterbi decoding to obtain the second reproduced data.
In one embodiment of this invention, a time from when the first reproduction section starts reproducing the data recorded in the recording medium until when the first reproduction section starts outputting reproduced data obtained by reproducing the data, is equal to a time from when the second reproduction section starts reproducing the data recorded in the recording medium until when the second reproduction section starts outputting reproduced data obtained by reproducing the data.
Thus, the invention described herein makes possible the advantage of providing an information recording and reproduction apparatus having a highly reliable verification operation.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.